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(1) Field of the Invention
This invention relates to a technique to provide high-resolution patterned images on each of obverse and reverse (generally top and bottom) surfaces of substrate panels using single-approach projection optics and a scanning stage, and more particularly relates to apparatus and method for flipping the substrate over, to provide access to a second surface of the substrate for pattern scanning, while retaining the registration and resolution advantages of having obverse and reverse of each substrate panel patterned in quick succession with the same projection optics scanned by the same stage carriage.
(2) Description of Related Art
State of the art microelectronics patterning systems follow the lead of U.S. Pat. No. 4,924,257, Scan and Repeat High Resolution Lithography System, Jain, May 08, 1990. Dr. Jain teaches the use of a treated beam of laser radiation for patterning a substrate according to a mask, both mask and substrate being scanned line-by-line by a small hexagonal field in overlapping complementary scans, for balanced illumination of the mask pattern on a photoresist on the surface of the substrate.
The desire to form such microlithographed patterns on both surfaces of a substrate, typically a thin, flat, non-flexible printed circuit board or microchip, is both stated and solved in U.S. Pat. No. 5,923,403. Simultaneous, Two-Sided Projection Lithography System, Jain, Jul. 13, 1999. Jain splits the radiation beam of a laser, and by light-beam directing projection optical systems applies patterning radiation simultaneously through separate masks to both sides of the flat substrate. The obverse and reverse surfaces of a substrate panel are simultaneously patterned by dual optical projection systems. One of the optical projection systems has an up-approach, through a see-through window in the stage carriage. The other optical projection system has a down-approach.
There is another way to divide the laser beam. U.S. Pat. No. 5,933,216, Double-Sided Patterning System using Dual-Wavelength Output of an Excimer Laser, Dunn, Aug. 3, 1999, splits the laser beam into two different peak-power wavelengths and forwards the separated beams along separate optical projection systems for the two sides of the substrate. The differing wavelengths of radiation require either a broadband photoresist or a separate photoresist for obverse and reverse, each optimized for a respective one of the two wavelengths. Two substrates may be accessed at one time, in one embodiment by up-approach and down-approach projection optical systemsxe2x80x94and in another embodiment by side-by-side down-approach projection optical systems, but for single sides only of the two substrate panels.
The two-sided projection lithography systems identified above provide for very high quality two-sided microelectronics patterning, mutually registered, with high throughput. They are most cost-effective in relatively long production runs. There remains, however, a continuing desire for simplicity and economy in two-sided high-resolution patterning, both aspects being economized by having single-approach optics and a simple stage carriage, with 1:1 projection optics, for mask and substrate.
The desire continues for a simple system for high-resolution patterning of two-sided substrates, which has a single set of projection optical system, provides easy two-side registration, and is economical for relatively short patterning runs.
It is the object of the invention to provide, in a novel microelectronics patterning system, electromechanical positioners to flip the substrates for economical two-side high-resolution patterning by a single set of projection optics.
Another object of the Invention is to provide a novel method for positioning and repositioning substrates for two-sided patterning, during a single production run, by flipping the substrates for patterning by a single-approach set of projection optics.
A feature of the invention is the use, in a simplified embodiment, of a single feeder/flipper/forwarder to load, flip, reposition and unload the substrate panels on the stage carriage which provides scanning motion of the substrates with respect to the projection optics and the masks.
Another feature of the invention is the use, in a second embodiment in which the economics favor separate feeders for loading and unloading, and a flipper/forwarder for repositioning the substrate after the first side has been patterned, for patterning the second side.
An advantage of the invention is that the costly portions of the system do not have to be replicated, but rather are time-shared as a result of the inventive hardware and method.
Another advantage is that there is no need for a see-through window in the stage carriage, allowing for simpler and more powerful substrate grasp by vacuum.
A significant advantage in economy arises from the ease with which this invention can be retrofitted on existing single-approach lithography systems, by alteration of programming in the control computer together with addition of relatively inexpensive flipper mechanisms to existing substrate feeder mechanisms, or by replacement feeder/flipper/forwarder mechanisms.